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# Solution Composition

“A solute plus solvent: solution.
We quantify its constitution:
Numeric relation;
Expressed concentration,
Decreasing upon its dilution.”

The 9 April 2022 Twitter limerick returned to far less dense material than the mechanistic deciphering of the last few verses and posts!  As the title suggests, this post (composition) translates a poem related to solution chemistry.

“A solute plus solvent: solution…”

A solution is a homogeneous (uniform) mixture of two substances: the substance present in the lesser amount is the solute, and the substance present in the greater amount is the solvent.

If we take one gram of table salt (sodium chloride, NaCl) and dissolve it in enough water to form exactly 150 mL of the solution, we generate an aqueous solution of sodium chloride: the salt is the solute and the water is the solvent.

“We quantify its constitution: /
Numeric relation; /
Expressed concentration…”

Chemists have several ways to quantify the constitution of a solution (to answer the question of how much solute and how much solvent will be present in the solution) and find its concentration.  Concentrations are calculated through “numeric relations,” or equations. The most common concentration expression is molarity: moles of solute divided by liters of solution (M = mol / L).

In the solution described above, 1.00 g of sodium chloride (NaCl) is equal to 0.0171 moles of NaCl, due to its molar mass of 58.4 g/mol. By taking 0.0171 mol NaCl divided by 0.150 L of solution, we obtain a molarity of 0.114 M here.

“Decreasing upon its dilution.”

If a solution is diluted, more solvent is added, while the amount of the solute stays the same.

For instance, in our example, if enough water is subsequently added to generate exactly 300 mL total, then the solution’s volume is doubled, and the molarity becomes half what it was: the solution’s concentration “decrease[s] upon its dilution.”

Some analogy likely applies here about how the clarity of this simpler post, compared to the last few, benefits from its succinctness (its “smaller volume”)!